As is well known, medical personnel must listen to and determine the heart rate of a patient in order to determine the condition of the patient. Standard or electronic stethoscopes are normally used to listen to a patient's heart and are formed with a detector which must be placed in contact with the skin of the chest of a patient. The heart rate is often determined by counting the number of heart beats over a period of time and multiplying the count by an appropriate factor.
There are situations, such as in the case of burn or trapped victims, in which the patients clothing cannot be removed. In such situations, it is necessary to listen to the patient's heart through the patient's clothing. This factor coupled with the likelihood of high background noise results in obscured heart sounds and considerable difficulty in accurately determining a patient's heart rate.
Standard stethoscopes require skin contact and therefore cannot be used in such a situation while electronic stethoscopes tend to produce high background electrical noise which further obscures the heart sounds. Neither provide a digital reading of heart rate. There are devices which can accurately measure heart rate from a patient's electrocardiograph but they tend to be bulky, heavy, expensive, require skin contact and complicated in use. Thus, there is a need for an easily operated, light, portable device which accurately reproduces heart sounds through several layers of clothing and provides a digital reading of heart rate.
Apart from distinguishing between heart sounds and extraneous or background noise, a device which measures heart rate must also account for the different heart sounds of which a heart cycle is comprised. More specifically, it is known that a heart beat or cycle is primarily comprised of two relatively closely spaced heart sounds. Assuming all extraneous and background noise could be removed and both heart sounds detected for each heart cycle, the heart rate could readily be determined simply by determining the time interval or period between three adjacent sounds and converting the period to a beats per minute (BPM) heart rate count. In practice, it is not possible to eliminate all background noise and detect both heart sounds of all cycles and thus this approach may provide inaccurate heart rate displays.